1. Field of the Invention
The present invention relates to a method of manufacturing a power transmission chain and a pretension load device used in a manufacture of the power transmission chain.
2. Related Art
For example, a power transmission chain with an endless shape used in a power transmission apparatus such as a pulley type continuously variable transmission (CVT) etc. of an automobile includes a link unit which is constituted by a plurality of link plates laminated in a width direction of the chain and a pin which connects the link plates of the link unit to each other (for example, see JP-A-2006-102784). A power is transmitted when both end surfaces of the pin engage with a pair of sheave surfaces of the pulley.
For example, as shown in JP-A-2006-102784, a strong tension to exceed a rated load is loaded on the power transmission chain during the manufacture so that a plastic deformation of the link plates occurs. Accordingly, a compressive residual stress is loaded thereon and work-hardening is provided in the link plate to improve a fatigue strength etc. Specifically, the chain is tensioned in the chain movement direction in the state where the chain is assembled in an endless shape so as to load the pretension.
However, in the case where the power transmission chain is configured such that the number of sheets of the link plates in each link unit is different or in the case where the power transmission chain is configured by using a plurality of link units of which the lengths of the link plates are different in the chain movement direction, plastic deformation amounts of the link plates tend to be non-uniform by loading the tension as described above. As a result, the compressive residual stress loaded on the link plates becomes non-uniform, and thus the strength improvement effect becomes non-uniform.
Additionally, the tension makes a large load that exceeds the rated load, and thus the end faces of the pin that receive the large load may be easily abraded.